Overhead conveyors are utilized in various production, assembly and treatment environments to transport parts or products through operational stages. Typically, such conveyors employ a rotating, generally horizontal tube or shaft that supports trolleys from which the load is suspended. Wheels on the trolleys ride on the surface of the rotating drive tube, and each is mounted for rotation about a driven wheel axis that is non-parallel and non-perpendicular to the drive tube axis, preferably at an acute angle to the drive axis. Often, there are various points in the path of the conveyor where a drive tube terminates, and the drive is then picked up by another drive tube spaced therefrom down the conveyor line. Separate drives may be required to rotate the separate tubes. As the trolleys may be spaced apart a distance greater than the space between the ends of the drive tubes, advancement of the trolleys (and thus the load suspended therefrom) is not interrupted by the spaced drives.
A switch is utilized when it is desired to selectively control the path of the trolley. At a switch, one drive ends and one of two drives spaced therefrom receives the advancing trolley depending upon the position of the switch. In this configuration the incoming drive is separately driven, as are each of the two receiving drives, thereby requiring separate drives at a two-position switch junction. Accordingly, three or more separate drives are required at a switch depending upon the number of switch positions.